Internal combustion engines are known for generating power that is used, for example, to drive a vehicle. In internal combustion engines, working fluids of the engine include air and fuel, as well as the products of combustion. Moreover, useful work is generated from the hot, gaseous expansion acting directly on moving surfaces of the engine, such as the crown of a piston, with reciprocating linear motion of the piston being converted into rotary motion of a crankshaft via a connecting rod or similar device.
Conventional internal combustion engines may be of a two-stroke or four-stroke type. In a conventional four-stroke engine, power is recovered from the combustion process in four separate piston movements or strokes of a single piston. In this type of engine, the piston moves through a power stroke once for every two revolutions of the crankshaft. On the other hand, in a conventional two-stroke engine, power is recovered from the combustion process in only two piston movements or strokes of that piston. In this type of engine, the piston moves through a power stroke once per revolution of the crankshaft.
Although two-stroke engines are known to have advantages over their four-stroke counterparts, their operation makes them somewhat undesirable in certain applications. For example, conventional two-stroke engines are known to have poor combustion control, which results in relatively high levels of emissions. In some cases, emissions associated with conventional two-stroke engines are too high to meet regulations addressing the emission of pollutants for vehicles. In addition, conventional two-stroke engines require the user to supply a mixture of fuel and oil in predetermined ratios in order to operate the engine, which may be inconvenient.
Accordingly, there is a need for a two-stroke engine that addresses these and other drawbacks associated with conventional two-stroke engines.